The present invention relates to a highly reliable gas-insulated switchgear and, more particularly, to a gas-insulated switchgear suitable for use as a puffer type gas-blast circuit breaker.
A general gas-insulated switchgear has a breaker including a stationary contact and a movable contact, a sealed vessel containing the breaker and filled with an insulating gas, such as sulfur hexafluoride gas (SF6), a contact operating device disposed outside the sealed vessel to operate the movable contact, a high-tension conductor connected to the breaker, an insulating spacer connected to the breaker, and buses.
It is possible that foreign matters are produced in the sealed vessel during the assembly of the gas-insulated switchgear or when the breaker exercises its function. If the foreign matters produced in the sealed vessel are conductive, it is possible that the dielectric ability of the insulating gas and the surfaces of insulators is deteriorated.
Various methods have been proposed to prevent the adverse effect of conductive foreign matters on the performance of the breaker in a case where the conductive foreign matters are produced in the sealed vessel. For example, a method proposed in JP-A No. 234113/1998 installs foreign matter catching vessels at a plurality of parts of a sealed vessel filled with an insulating gas and holding a breaker therein, corresponding to nodes of vibration to catch foreign matters when the sealed vessel is shook by the circuit-breaking action of the breaker.
Foreign matters produced in the sealed vessel tend to gather in the nodes of vibration. Therefore, the foreign matters are caught efficiently by the foreign matter catching vessels disposed at the nodes and, consequently, the deterioration of the dielectric ability by conductive foreign matters can be prevented.
However, the prior art method does not give any consideration to a fact that the sealed vessel of the gas-insulated switchgear needs many incidental devices, and have problems in manufacture and cost. Although the prior art method disposes the foreign matter catching vessels at the nodes of vibration, the gas-insulated switchgear needs an absorbent to be placed in all the gas compartments, and the gas-insulated switchgear must be provided with a hand hole for inspecting the breaker.
Nevertheless, the prior art method does not give any consideration to providing the absorbent and forming a hand hole. Thus, some other parts for holding the absorbent must be formed by connecting branch pipes or the like to the sealed vessel, which makes the construction of the gas-insulated switchgear complicated and invokes problems in manufacture and cost. Many branch pipes connected to the sealed vessel spoils the appearance of the gas-insulated switchgear.
Accordingly, it is an object of the present invention to provide a gas-insulated switchgear capable of being easily and economically manufactured and of facilitating work for maintenance and inspection, and excellent in electrical insulating performance.
A gas-insulated switchgear according to one aspect of the present invention includes a sealed vessel filled with an insulating gas; a circuit breaker held in the sealed vessel; and a branch pipe attached to a lower part of the sealed vessel right below the circuit breaker; wherein the branch pipe defines a hand hole for use in inspecting the circuit breaker, provides a place for installing an absorbent container and forms a foreign matter collecting space.